WO2010006781A1 - Method for calibrating a position sensor in a motor vehicle gear - Google Patents

Abstract

Method for calibrating a position sensor in a motor vehicle transmission comprising a gear housing with a housing (10) included therein for the position sensor, said sensor housing comprising a pressure member (14) that is held moveably inside the housing (10), said member being pre-stressed elastically against a switch bump and comprising an electric path sensor (38) actuated by the pressure member (14) for measuring the position of the pressure member (14) relative to the housing (10), characterized in that after the housing (10) of the position sensor is installed into the gear housing, at least one calibration measurement is carried out by the path sensor (38) for at least one gear position and for the associated measured value of the path sensor a tolerance zone is defined for each gear position to be detected using the results of the respective calibration measurement.

Description

 METHOD FOR CALIBRATING A POSITION SENSOR IN ONE

MOTOR VEHICLE TRANSMISSION

The invention relates to a method for calibrating a position sensor in a motor vehicle transmission.

From DE 43 07 596 C2 a locking device for manual transmission is known, with a movably held in a housing pressure member which is resiliently biased in a protruding from the housing position, and with a nem actuated by the pressure member electrical signal generator. This locking device serves to lock a switching shaft of the gearbox in the selected position. The pressure member is resiliently biased against a shift mountain formed on the shift shaft and able to engage in various depressions of the switch mountains, each corresponding to a certain switching position. In the housing, a switch is integrated as a signal generator, which serves as a reverse light switch and is always closed when the pressure member is in the locking recess for reverse gear.

From DE 195 09 878 C l a similar locking device is known, which in addition has a tolerance compensation mechanism, which makes it possible to automatically compensate for any tolerances in terms of the shape of the switch mountain and the installation position of the housing of the latching device.

If, as described in DE 10 2005 034 864, the signal transmitter is a displacement sensor for measuring the position of the pressure member relative to the housing, it is possible in principle, different depths of the wells in the switch mountains, in which the pressure member is in each case, quantitatively To measure and thus to detect the respective shift position of the transmission based on different depths of the locking recesses. In this way, not only a specific shift position can be scanned, such as the reverse gear, but by quantitative evaluation of the signal of the signal generator can be distinguished between several different shift positions of the transmission. Thus one obtains a position sensor with which different gear positions can be detected, for example, in addition to the reverse gear and the neutral position of the transmission. The object of the invention is to provide a method for simple and accurate calibration of such a position sensor.

This object is achieved in that after installation of the housing of the position sensor in the gear housing with the displacement sensor at least one calibration measurement is performed for at least one gear position and based on the result of this calibration measurement for each to be detected gear position defines a tolerance zone for the associated measured value of the displacement sensor becomes.

With a sensor that is calibrated according to this method, the decision as to which position the gearbox is currently in remains reserved for special evaluation electronics, which need not necessarily be part of the sensor itself. The sensor supplies to this evaluation electronics only the result of the distance measurement, and if this result is within one of the tolerance zone defined in the calibration, the evaluation electronics detects that the transmission is in the position belonging to this tolerance zone. Since the calibration measurement takes place only after the installation of the housing of the position sensor in the gear housing, can be eliminated by the calibration all tolerances that have an influence on the result of the distance measurement.

Advantageous embodiments of the invention are specified in the subclaims.

According to an advantageous embodiment of the invention takes place in the course of the service life of the transmission constantly or at least from time to time recalibration. If aging or wear leads to the fact that measured for the various gear positions paths of the pressure member have a temporal drift, this can be determined by comparing the temporally successive measurement results and the tolerance zones can be readjusted accordingly. If it turns out that the tolerance zones for two different gear positions approach each other and threaten to overlap one another, a warning signal can be output and thus a repair of the relevant gear components can be initiated. The inventive method is particularly advantageous in vehicles with a start / stop system, in which also has to be recognized whether the transmission is in a driving position or in the neutral position. Likewise, the invention makes it possible to detect other switch positions, such as those for the first gear, the second gear, etc., and thus to give the driver feedback about the respectively set gear position. In addition, the position sensor can of course also serve as reversing light switch as before.

Since it is possible with the aid of the calibration method to eliminate the influences of virtually all tolerances, the differences in the levels of the gearshift for the different gear positions can be chosen very small. This has the advantage that the force with which the pressure member is biased against the switch mountains, for the various gear positions is almost equal, so that the driver always feels essentially the same locking resistance, regardless of which gear he just inserts.

In the following, an exemplary embodiments are explained in more detail with reference to the drawing.

Show it:

1 shows an axial section through a locking device, which also forms a position sensor for a motor vehicle transmission.

Figure 2 is a partial view of the latching device in conjunction with a switching shaft shown in section.

3 shows a diagram for explaining the evaluation of the signal of a displacement sensor of the latching device;

4 shows a section through a transmission with a position sensor according to another embodiment; and

Fig. 5 is a flowchart for the inventive method. A latching device shown in Fig. 1 comprises a housing 10 in the form of a so-called locking screw, which has an external thread 12, with which it can be screwed into a not shown here housing a gearbox. At the projecting into the gear housing end of the housing IO as a pressure member 14, a detent ball is arranged, which is mounted with low friction support balls 16 in a bearing shell 18 and secured by a retaining ring 20. The bearing shell 18 forms the end of a cylindrical sleeve 22, which is mounted in a ball bearing 24 and axially movable within a limited range in the housing 10. An outer race for the balls of the ball bearing 24 is formed by a pressed into the housing pot 26 of deep-drawn and hardened sheet metal, which is held at its open lower end by a cone ring 28 and its closed except for a central opening upper end of an abutment for a spring 30 forms. The spring 30 extends axially within the sleeve 22 and is supported at its lower end on the bearing shell 18. The spring 30 surrounds a coaxially inside the sleeve 22 formed inner tube 32 which carries at its upper end a magnet 34 (permanent magnet), which projects upwardly out of the opening of the pot 26.

In the upper end of the housing 10 is a cap 36 shown in the drawing, only partially used in plastic, in which a magnetic displacement sensor 38, such as a Hall sensor, is held so that it is opposite to the upper end of the magnet 34 at a distance. Electrical contacts 40 of the displacement sensor 38 are led up out of the cap 36.

The displacement sensor 38 responds to the magnetic field of the magnet 34 and is capable of measuring the distance between the magnet 34 and the displacement sensor 38 with high precision, for example with an accuracy of a few μm. Thus, a multi-valued, for example analogous, electrical signal can be tapped at the contacts 40, which signal indicates the axial position of the magnet 34 precisely. In Fig. 1, various possible positions of the magnet 34 are indicated by dashed lines. The analog signal of the position sensor 38 can then optionally evaluated by an analog electronic circuit or first digitized and then further evaluated by a digital electronic circuit. In the example shown, thus, the displacement sensor 38 is a non-contact sensor, which has the advantage that wear and contamination problems are avoided. In addition, it is possible to separate the mechanical part of the latching device by a thin partition or membrane 42 made of non-magnetic material from the displacement sensor and so encapsulate the mechanical part of the locking device and at the same time to protect the displacement sensor 38 against contamination.

Instead of a Hall sensor, other non-contact sensors can alternatively be used as the displacement sensor 38, for example an inductive sensor or even a capacitive sensor. In these cases, the magnet 34 could be replaced by an electrically conductive body.

In Fig. 2, the lower part of the housing 10 and the pressure member 14 are shown in conjunction with a switching shaft 44 of a motor vehicle transmission.

The switching shaft 44 carries a switching mountains 46 with three recesses formed in different peripheral areas, which are designated here by I, II and III and which are separated from each other by elevations 48 of the switch mountains. Depending on the switching position of the transmission, the pressure member 14 engages in one of the recesses, in the example shown in the recess II.

Although this is not shown in the drawing, the recesses I, II, III (and possibly further, not shown depressions) may also be designed so that the pressure member 14 not only causes a detent in the direction of rotation of the shift shaft 44, but also in the axial direction.

The three recesses I, II and III differ in their depth. In Fig. 2, the radii of the bottom of the depression are each shown in dashed lines. Each shift position of the transmission thus corresponds to a recess with a different depth and accordingly a different axial position of the pressure member 14 and thus a different distance between the magnet 34 and the displacement sensor 38 in Fig. 1. In the example shown, for example, the recess I to the reverse gear , the recess II of the neutral position of the transmission and the recess III be assigned to the other gear ratios of the transmission. Optionally, by a correspondingly greater number of depressions, which are arranged in the circumferential direction or in the axial direction on the shift shaft can also be a differentiation of the various forward driving levels possible.

In Fig. 3 shows schematically how the signal of the displacement sensor 38, which indicates the position of the magnet 34, can be electronically evaluated to detect the respective state of the gearbox. In Fig. 3, the magnet 34 is shown in solid lines in its lowest position corresponding to the recess I. The positions corresponding to the other depressions are indicated by dashed lines. Each of these positions is assigned a specific value of the signal of the displacement sensor 38. If the value actually measured by the travel sensor 38 differs from the position by exactly less than a certain tolerance, which should correspond exactly to the depression I, that is to say lies in a tolerance zone which is designated 50 in FIG. 3, then the evaluation electronics recognizes that the pressure member 14 is engaged in the recess I (reverse gear). Accordingly, the recess II or III is detected when the measured value is in the zone 52 or 54. However, the tolerance zones are separated by certain "forbidden zones" in which the measured signal can not be clearly assigned to a specific gear position. In this way, a secure and robust detection of the respective transmission state is possible. If the measured value is not in one of the zones 50, 52, 54, then the signal is considered not evaluable, and if this condition lasts longer, an error message can be issued.

The location of the tolerance zones 50, 52 and 54 relative to each other is determined by the machining of the shifting mountain 46 and is therefore known with sufficient accuracy for a given gear train. The absolute location of these zones is also dependent on the installation position of the housing 10 in the transmission housing and therefore may vary slightly from gearbox to gearbox. However, these variations can be compensated by the fact that after installation of the housing at least one measurement for one of the wells I, II or III is performed and the position of the tolerance zones 50, 52, 54 is calibrated accordingly.

While in the exemplary embodiment described so far, the gear position sensor also forms a latching device for the mechanical locking of the gearshift shaft, it is optionally also possible to adjust the functions of the positioner. onsmessung and the detent to separate. As an example, Fig. 4 shows a section through a gear housing 56, in which the shift shaft 44 is mounted, which in turn carries the switching mountains 46. Here, the gear housing 56 takes on one hand a position sensor 58 and on the other hand a latching device 60 at two positions diametrically opposite each other with respect to the selector shaft 44. The position sensor 58 and the latching device 60 each have a pressure member 14 which is biased against the switching mountain 46, and may be constructed identically, except that the latching device 60 does not need to have a displacement sensor.

On the side of the latching device 60, the shift gear 46 forms an axial guide groove 64 in which the pressure member 14 engages, so that the shift shaft 44 is locked in its angular position while being movable in the axial direction (eg, to select the shift gate). When the selector shaft 44 is rotated about its axis in a given axial position to select a particular gear, the pressure member 14 of the position sensor 18 scans various plateaus 66 on the side of the gearshift 46 facing the position sensor, each one geared are assigned and differ in their height. The respectively selected gear position is detected by using the displacement sensor 38 'in the position sensor 58, the height of the respective plateau is measured.

The construction shown in Fig. 4 with opposite arrangement of position sensor 58 and latching device 60 has the advantage that exerted by the compression members 14 elastic forces cancel each other, so that the shift shaft 44 is better balanced.

As a displacement sensor 38 ', an inductive sensor is provided in this example, the signal of which is evaluated in an evaluation electronics 68 arranged directly in the housing 10. The evaluation electronics also includes a temperature sensor 70 which measures the current temperature of the transmission and position sensor 58. On the one hand, the measured temperature can be used to compensate thermal expansions of those transmission and sensor components which would distort the result of the displacement measurement, but it can also be used for the known temperature drift of the inductive displacement sensor 38 'and possibly other components compensate the evaluation electronics 68 selbsst. Generally This concept allows the use of displacement sensors, which need only have a low temperature stability.

During the assembly of the transmission shown in FIG. 4, the shift bellows 46 is first mounted on the shift shaft 44 and then the shift shaft is installed in the transmission housing 56 and stored there with bearings, not shown. The housing of the position sensor 58 and the latching device 60 are then installed in the respectively provided position in the transmission housing 56, for example screwed or pressed. Only at the end of the assembly line, when at least all those components of the transmission are mounted, which can influence the movement of the pressure member 14 in the position sensor 58, this position sensor is calibrated. In this way it is achieved that all relevant tolerances are eliminated during calibration, for example tolerances of the bearings for the shift shaft 44, ToIe- tolerances in the assembly of the shift mountain 46 on the shift shaft and tolerances in the installation of the position sensor 58 in the transmission housing 56th

In Fig. 5, the various assembly and calibration steps are shown in a flow chart. The order of the assembly steps S l to S3 is not mandatory. It is only important that these assembly steps take place before step S4, in which the calibration measurements are made. In the calibration measurements, the position of the pressure member relative to the housing 10 in each gear position, i. , measured for each plateau 66. Appropriately, the switching shaft is repeatedly moved between the various gear positions, and there are several measurements, so that can be suitably determined based on the results not only the positions of the corresponding tolerance zones, but also the widths of the tolerance zones based on the scatter of the measurement results (see FIG. 3).

In the course of the service life of the gearbox wear on the pressure members 14 and the corresponding contours of the gearshift 46 may occur so that move the individual transmission positions associated tolerance zones. Corresponding displacements can also result from other effects, such as thermal expansion of the gear housing 56 and the like. In the method proposed here, therefore, after the actual calibration with the storage of the tolerance zoom is completed in step S5, provided during the operating life of the transmission, a continuous recalibration. In step S6, a position measurement is performed, in which the position of the pressure member is determined relative to the housing. The evaluation electronics then compares the measurement result with the stored tolerance zones and reports the gear position determined in this way to a higher-level supervisory authority. Furthermore, in the evaluation electronics from the current position measurement and one or more previous position measurements for the same gear position, a moving average is formed, and based on this moving average and possibly on the basis of the measured dispersion of the measured values, the tolerance zone for this gear position is recalculated in step S7. Accordingly, one also proceeds with the other gear positions. The steps S6 and S7 are then cyclically repeated during the operating period of the transmission, for example, after each switching operation or each after a certain number of switching operations or after a certain period of operation.

Claims

A method of calibrating a position sensor (58) in a motor vehicle transmission having a transmission housing (56) incorporating a housing (10) for the position sensor comprising a resilient member (14) movably retained in the housing (10) is biased against a switch ring (46) and has an electrical displacement sensor (38, 38 ') actuated by the pressure member (14) for measuring the position of the pressure member (14) relative to the housing (10), characterized in that after installation the housing (10) of the position sensor (58) in the gear housing (56) with the displacement sensor (38; 38 ') at least one calibration measurement is carried out for at least one gear position and on the basis of the result of this calibration measurement for each gear position to be detected a tolerance zone (50, 52, 54) is defined for the associated measured value of the displacement sensor. 2. The method of claim 1, wherein at least one calibration measurement is carried out for each to be detected gear position. 3. The method of claim 1 or 2, wherein the tolerance zones (50, 52, 54) are continuously corrected during operation of the motor vehicle transmission based on the results of current position measurements. 4. A method according to any one of the preceding claims, wherein the temperature of the transmission case (56) is measured and the result of the displacement measurement is corrected for thermal expansion of transmission and / or sensor components. 5. The method according to any one of the preceding claims, wherein in which the temperature of the displacement sensor (38) is measured and the result of Distance measurement is corrected with respect to a Tempraturdrift the displacement sensor. 6. The method according to claims 4 and 5, wherein the temperature of an integrated into the housing of the position sensor (58) evaluation electronics (68) is measured as representative of the temperature of the position sensor (58) and the transmission housing (56) representative temperature. 7. The method of claim 5 or 6, wherein as the displacement sensor (38 '), an inductive sensor is used.